Post scarcity is a bad phrase. After the invention of industrial farming we basically already have a semi post scarcity as far as cheap caloric energy is concerned.

Marx was right that the basic means of survival: water, shelter, food are becoming so inexpensive that we have a problem: hording of resources. That's about where I part with Marx though because I think that human nature shows we will always have scarcity even in a very advanced society because humans become dependent and entitled to their living standards. So dependent they are willing to kill for them.

So in a way I think that social Utopia will never be achieved and if it was humans would hate it and destroy it because humans naturally crave inequality, hierarchy, meritocracy, etc. This is the primary misunderstanding of human nature that marx made.